I have a 1991 Trans Am Conv. with the stock 305. It is a 5 spd. Standard tranny. 68,000 miles. All original components as far as I know.

When out of gear at idle the rpm gage moves up and down.

I had a new module, IAC motor and oxygen sensor put on. The coil was checked and is OK. I also ran some BG K44 fuel additive to clean the engine of carbon build up.

The idle is a little better than before. Before it was so bad the car would stall. It is not stalling now and has lots of power. Just the fluctuating rpm.

Has anyone else had this problem? If so, how did you fix it?

Thanks.

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Sean

1977 S/E TA
1980 Conv. Turbo TA
1989 TTA
1991 Conv. TA

 

Could be a number of things, check your temp sensor. My car when I first converted it to TPI had what sounds like the same problem. If the temp sensor has gone funky then the ECM is not getting the correct reading. (Mine was located on the front of the intake-base)

You can check it with a scanner to be sure. Keep note of it, does it only occurr when it is cold, hot, in certain temp ranges??? If that is the case then you have a bad temp sensor. Mine would run fine once it was warm, but getting there was nothing more than a struggle. Changed the sensor, and then no more problems.

I checked the sensor with an OHM meter and it looked good, When I pulled it out it stopped working completely


John

 

Try to adjust the TPS, when its surging open the hood and adjust the tps a little ( more volts...) and wait and se if it gets better. I had to do that today on my 383. The idle went from 400-2000 rpm and I andjusted the TPS a little ( dont know how much) and it Idles great!! Worth a try....

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GTA -89:Free flow muffler,dual 3" HF cats, Edelbrock headers, Vette heads, 1.52 RR 7/16, ZZ-9 cam, Big Mouth, AS&M LTR, !plenum, 52 TB, MSD 6AL, TPIS level V prom, Superior shift-kit and all the minor mods, a Canfield headed 383 in the works!! ready May 2001...ok..june...july..and with Accel DFI....looking for SR or miniram....
http://www.itv.se/tacs/members_cars/m279/m279.html (Swedish Trans Am Club)

 

Thanks guys.

I think the temp sensor was changed, but I'll check. Seems like it gets worse the hotter the car gets.

Actually the fluctuation is only a few hundred rpm so even if I can't fix it it is tolerable. Just wondering why it is not steady.

Thanks for the input.

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Sean

1977 S/E TA
1980 Conv. Turbo TA
1989 TTA
1991 Conv. TA

 

three letters. EGR. mine did the same thing until i replaced the egr solenoid. it was stuck open pumping exaust into the intake at idle which is a big no no.

 

Definately check the TPS voltage first.

 

Thanks guys.

I had the egr valve replaced. It was in fact sticking. But I still have the problem.



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Sean

1977 S/E TA
1980 Conv. Turbo TA
1989 TTA
1991 Conv. TA

 

I have the same problem. some times it will act up alot and some time it is reasonably smooth I just changed the EGR valve today no better. I think the next thing is a solenoid.

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91 Z28 5.7l Camaro
T-56,McLeod Street Clutch, Cross Drilled Brakes, KYB's,AFPR, 3.73 Gears, Borla Adjustable Cat Back, Hypertech Chip, Hooker Headers.
more to come....
My 91 Z28

 

Which solinoid do you plan to replace?

I'm also running some BG K44 fuel additive. Need to get it through the system now.




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Sean

1977 S/E TA
1980 Conv. Turbo TA
1989 TTA
1991 Conv. TA

 

I am planning on replacing my EGR solenoid the one that directs the vaccum to the egr valve.

 

Please let me know what happens.

Thanks.